1. Field of the Invention
The present invention relates to a tire pressure detecting apparatus installed in a vehicle to detect tire pressures.
2. Description of the Related Art
In recent years, vehicles provided with pneumatic tires have tended to be equipped with tire pressure detecting apparatuses for the improvement of driving safety which detect tire pressures, transmit the detected tire pressures to ECUs (electronic control units) arranged in the vehicles, and notify persons in the vehicle of the tire pressures.
An example of a tire pressure detecting apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 2001-322411. This related art arranges a tire pressure sensor with a transmitter on each tire of a vehicle. Tire pressure data measured with the sensors is transmitted on radio waves. The tire pressure data is received by a receiver through antennas that are arranged for each tire, respectively. The data is then displayed on a display unit installed in the vehicle.
According to the related art, the single receiver receives tire pressure data for all tires (four in a four-wheel vehicle) transmitted from the tire pressure sensors that are arranged on each tire, respectively. This receiver has difficulty identifying which data corresponds to which tire. Namely, the related art may detect an abnormal tire pressure but is difficult to tell which of the tires has caused the abnormality.
To solve this problem, there is an idea that allocates an ID for each tire pressure sensor installed on each tire of a vehicle and reads the IDs through a receiver. This technique may identify the respective IDs of the sensors to distinguish the tires themselves from each other but is unable to specify the respective positions of the tires in the vehicle based on the sensor IDs. When a tire rotation is carried out to change the positions of the tires in the vehicle, it is difficult for this idea to specify the positions of the tires in the vehicle based on the IDs. In most cases, the driver of a vehicle expects to know the pressure of a given tire and the position thereof in the vehicle instead of identifying the tire itself.